The project is designed to use sophisticated data management methods to develop new NLSY kinship linking files, which will be broadly valuable to demographic, developmental, and behavior genetic researchers, as well as to broader social/behavioral science researchers. We propose to create data files from newly available kinship information in two of the National Longitudinal Survey databases, the National Longitudinal Survey of Youth 1979 data (the NLSY79, a probability sample of adolescents aged 14-22 in 1979), and the National Longitudinal Survey of Youth Children data (the NLSYC, a survey of all biological children born to females in the NLSY79). We will create sibling pair files and multi-level files using the NLSY79 and the NLSYC. Our extensive background creating kinship linking files using implicit kinship links in the three past NIH-funded projects provides us unique experience and talent to develop these files, to circulate them to research teams, and to provide technical support to facilitate their use in applied research settings. The product of this effort will be the production of four kinship link files in a variety of formats, a web-based system available to access the files, and training of a new young researcher to provide technical support in the use of these files. We document the value of these files to dozens, and potentially hundreds, of research teams who conduct family research using the NLSY datasets.